Bumblebees are important pollinators in gardens

Last Updated:

February 28, 2008

"Humanity, for its own sake, must attend to the forgotten pollinators and their countless dependent plant species." -- E. O. Wilson, insect ecologist and author

CORVALLIS - The Pacific Northwest has 16 species of native bumblebees. Luckily, these fuzzy pollinators have not been affected by the two species of parasitic mites that have knocked back honeybee populations.

Bumblebee populations are thriving in the Pacific Northwest. They play a crucial role in pollinating native plants, gardens and crops.

Large and robust, bumblebees are fuzzy, brightly colored, and usually black contrasting with yellow, but sometimes red or orange, explained Lynn Royce, insect identification specialist with the Oregon State University Extension Service.

As industrious as honeybees, bumblebees collect nectar and pollen from a wide variety of plants. They are excellent pollinators of vegetables, flowers, and fruit trees and are essential to pollination and fruit set of commercial and home crops including many types of berries. Greenhouse growers introduce bumblebees into greenhouses to pollinate tomatoes.

Each species of bumblebee has a different range of flowers that it pollinates, but the different species together are usually capable of pollinating many of the plants in a flower or vegetable garden.

Bumblebees are the only native bees that are social. That is, they live in colonies, usually of less than 100 individual bees, and different bees perform different tasks for the colony. Their social behavior is not as complex as honeybees, says Royce. And they can sting.

In the late fall of each year, a new queen bumblebee hibernates. She is the only bumblebee from the colony to survive the winter. In spring, the new queen awakes and searches for a new nest site. The old queen dies in the fall, after a season of laying eggs.

Some types of bumblebees prefer a well-insulated cavity in the ground, such as an abandoned mouse nest. Others species find suitable sites above ground. All types of bumblebees prefer nests to be warm, dark, and undisturbed. The OSU Extension Service gets a lot of calls regarding bumblebees in birdhouses, said Royce.

As a bumblebee colony grows over the summer, new generations replace older generations. Bumblebees only live for about a month and spend the vast majority of their time foraging for nectar and pollen to eat and feed the next generation.

Bumblebees are more active early in the morning and late in the day than any of our other bees. They can carry 90 percent of their body weight in nectar in their "honey stomach" and 20 percent of their body weight in pollen in the pollen baskets on their hind legs.

Most gardeners will find bumblebees in their gardens naturally. Plants that they are particularly attracted to include lupine, mint, larkspur, aster, clover, salmonberry, Oregon grape, salal, blueberry, madrone and rhododendron. Bumblebees will look for hedgerows and other undisturbed areas to build their nests.

Some writers advocate that home gardeners build artificial nests for bumblebees of wood and a small amount of PVC pipe and place them in quiet places in the garden. Royce says that very few of these structures are ever accepted by searching bumblebee queens.

To learn more about bumblebees, visit Utah State University's Website on bees: http://www.loganbeelab.usu.edu/. Bumblebee populations are thriving in the Pacific Northwest. They play a crucial role in pollinating native plants, gardens and crops. Industrious bumblebees collect nectar and pollen from a wide variety of plants. They are excellent pollinators of vegetables, flowers, and fruit trees and are essential to pollination and fruit set of commercial and home crops such as including many types of berries.

For more information on "Gardening with Beneficial Insects," PNW 550, visit our on-line catalog. Our publications and video catalog at: http://extension.oregonstate.edu/catalog/ shows which publications are available on the Web and which can be ordered as printed publications.